Studies indicate a lower occurrence of diabetes mellitus (DM) in patients with neurofibromatosis type 1 (NF1). Fasting blood glucose (FBG) level is the main criterion used to diagnose DM and glucose intolerance. Therefore, this study compared FBG level between adults with NF1 and non-NF1 controls. We selected clinical records of 57 out of 701 individuals attending the Neurofibromatosis Outpatient Reference Center of the Clinics Hospital of the Federal University of Minas Gerais in Brazil. The selected patients with NF1 were matched to non-NF1 controls selected from the Brazilian Longitudinal Study of Adult Health according to sex, age (range, 35–74 years) and BMI at a ratio of 1:3. In both groups, individuals with DM were excluded. Median FBG level in the NF1 group (86 mg/dl (range, 56–127 mg/dl)) was lower than that in the non-NF1 control group (102 mg/dl (range, 85–146 mg/dl)) (P<0.001). Prevalence of FBG level ≥100 mg/dl in the NF1 group (16%) was lower than that in the non-NF1 control group (63%) (P<0.05). The chance of a high FBG level was 89% lower in the NF1 group (odds ratio, 0.112; 95% CI, 0.067–0.188) (P<0.05). In conclusion, adults with NF1 showed a lower FBG level and a lower prevalence of high FBG level compared with non-NF1 controls.